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    Design of highly selective, and sensitive screen-printed electrochemical sensor for detection of uric acid with uricase immobilized polycaprolactone/polyethylene imine electrospun nanofiber
    (Pergamon-Elsevier Science Ltd, 2023) Muhammad, Fakhriy; Dik, Gamze; Kolak, Seda; Gedik, Kubra Karadas; Bakar, Busra; Ulu, Ahmet; Ates, Burhan
    Uric acid (UA) plays a significant role in nerve center, human metabolism, and kidney system. Therefore, it is necessary to establish a simple, rapid, and sensitive detection method for UA. In recent years, researchers have been highly attracted by nanomaterials with satisfactory functions in electrochemical applications. In this study, polycaprolactone (PCL)/polyethylene imine (PEI) nanofiber membranes were prepared and used for the immobilization of uricase (UOx). The prepared membranes were characterized in terms of structure, composi-tion, and morphology. Afterward, the quantum dot screen printed electrode (QD SPCE) was modified with PCL/ PEI nanofiber membranes with and without methylene blue (MB) as an electron mediator. The electrochemical performance of the developed sensors was investigated by cyclic voltammetry (CV), differential pulse voltam-metry (DPV), and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, the modified sensors provided a broad linear range (5.0-52.0 mu M) for the electrochemical detection of UA. Limit of detection (LoD) values were determined as 3.96 mu M and 1.85 mu M for the PCL/PEI/UOx/QD SPCE and PCL/PEI/UOx/MB/ QD SPCE, respectively. The four-week stability results showed the change in current for the PCL/PEI/UOx/QD SPCE and PCL/PEI/UOx/MB/QD SPCE to be 92% and 87%, respectively. Additionally, in the mixed interference test remaining current ratios for UA were 95% and 82% for the PCL/PEI/UOx/QD SPCE and PCL/PEI/UOx/MB/ QD SPCE, respectively. Most importantly, the effectiveness of the electrodes was also verified in real sample detection with satisfactory recovery (similar to 98-112%). Overall, the results showed that the PCL/PEI/UOx/QD SPCE and PCL/PEI/UOx/MB/QD SPCE have the advantages of simplicity, high sensitivity, and good selectivity for UA determination.
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    Detection of Diazinon Organophosphates Using Magnetoelastic Sensor
    (Ieee-Inst Electrical Electronics Engineers Inc, 2022) Atalay, Selcuk; Ates, Burhan; Balcioglu, Sevgi; Inan, Orhan Orcun; Kolak, Seda; Simsek, Murat; Kolat, Veli Serkan
    In this study, 2826MB (Fe40Ni38Mo4B18) amorphous ferromagnetic ribbons were used as a magnetoelastic sensor (MES) to detect diazinon organophosphates (OP). Since enlarging the sensor surface area makes a significant contribution to the sensitivity of the sensor, nanofibers were coated on the sensor surface, and then, the nanofibers were functionalized with glutaraldehyde (GA) in order to covalently bind acetylcholinesterase (AChE) enzyme to the surface. It was found that binding of OPs to the AChE enzyme at the functional amorphous ribbon surface, a large change in the resonance frequency was observed. The results showed that functionalized MES shows a linear change according to the amount of OP detected in the range of 0-140 nL or 0-150 ppm in the solution.
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    Diagnosis, Bacterial Density, Food, and Agricultural Applications of Magnetoelastic Biosensors: Theory, Instrumentation, and Progress
    (Springer, 2024) Balcioglu, Sevgi; Inan, Orhan Orcun; Kolak, Seda; Ates, Burhan; Atalay, Selcuk
    Magnetoelastic biosensors have emerged as a promising technology for the sensitive and label-free detection of a wide range of biological analytes. These biosensors use the magnetoelastic effect, which describes how the mechanical properties of magnetostrictive materials change in response to a magnetic field. This effect is utilized to detect biological analytes by immobilizing specific recognition elements, such as antibodies or nucleic acids, on the magnetoelastic material's surface. The binding of target analytes to the recognition elements induces a mass change, leading to a shift in the resonance frequency of the magnetoelastic material. Magnetoelastic biosensors find applications across various fields, including medical diagnostics, environmental monitoring, and food safety. In medical diagnostics, they offer rapid and sensitive capabilities for detecting pathogens, biomarkers, and toxins. For environmental monitoring, they demonstrate the ability to detect pollutants and heavy metals. Furthermore, in ensuring food safety and quality, magnetoelastic biosensors detect allergens, pathogens, and contaminants effectively. Ongoing research and technological advancements suggest that these biosensors hold great potential for revolutionizing various fields, including healthcare, environmental monitoring, and food safety, contributing to improved disease diagnosis, environmental protection, and public health. This review article provides an overview of the principles, fabrication methods, diagnosis, bacterial density, food, and agricultural applications of magnetoelastic biosensors.
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    Fabrication of electrospun polycaprolactone/chitosan nanofiber-modified screen-printed electrode for highly sensitive detection of diazinon in food analysis
    (Elsevier Sci Ltd, 2022) Topsoy, Oguz Kagan; Muhammad, Fakhriy; Kolak, Seda; Ulu, Ahmet; Gungor, Oznur; Simsek, Murat; Koytepe, Suleyman
    In the present study, a screen-printed electrode for Diazinon (DZN) detection was modified with nanofibers prepared via electrospinning technique. The chemical structure, morphology, and crystallinity of the nanofibers were characterized in detail. The electrochemical behaviors of the modified screen-printed electrode were evaluated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The spinning time, pH value and scan rates were optimized at 6 min, 5.25, and 50 mVs(-1), respectively. The limit of detection as 2.888 nM was obtained over a linear concentration range (3 nM-100 nM). Besides, DZN selectivity, repeatability, and storage stabilities of the developed sensor were proven. Meanwhile, the sensor was successfully applied for the determination of DZN in the tomato juice sample with recovery values in the range of 93.27-108.30%. The developed sensor could be a promising candidate to detect the presence and level of DZN in real samples.
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    Preparation of 10-undecenoic acid based polyurethane/PCL fibers by electrospinning method and investigation of their antifungal properties
    (Springer, 2022) Acari, Idil Karaca; Boran, Filiz; Kolak, Seda; Tatlici, Eray; Yesilada, Ozfer; Koytepe, Suleyman; Ates, Burhan
    Nowadays, in the treatment of such fungal infections, antifungal drugs in various forms are one of the most preferred methods. These medications can be in the form of creams and lotions, shampoos, pills, suppositories, powders, or sprays. The dose of the drugs is adjusted according to the type and growth area of the fungus, the severity of the symptoms, and the medical history of the patients. Dressing materials with antifungal properties are an alternative treatment method used for the treatment of fungal skin infections. These covers not only treat fungal infections but also prevent their spread. Within the scope of this study, polyurethane-based wound dressing materials (PU-UDA/PCL) with antifungal properties were developed. Electrospining method was used to produce these dressing materials and the surface area of the wound dressing material was increased, thereby increasing the effect of antifungal property. Polypropylene glycol, glycerol, and catechin as polyol were preferred in polyurethane (PU) synthesis. These structures were polymerized with isophorone diisocyanate and modified with 10-undecenoic acid. Obtained 10-undecenoic acid modified polyurethane (PU-UDA) structures were transformed into wound dressing structure with polycaprolactone (PCL) by electrospinning method. Structural, morphological, and thermal properties of the wound dressing materials were analyzed with different instrumental analysis methods. The antifungal activities of PU-UDA/PCL were tested. Antifungal tests were performed on C. albicans and C. tropicalis. Therefore, PU-UDA/PCL series could be used as an efficient antifungal agent. Finally, it was determined that the obtained 10-undecenoic acid-based polyurethane fibers have a suitable structure and feature for the treatment of many fungal infections.
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    Tailor-made novel electrospun polycaprolactone/polyethyleneimine fiber membranes for laccase immobilization: An all-in-one material to biodegrade textile dyes and phenolic compounds
    (Pergamon-Elsevier Science Ltd, 2023) Kolak, Seda; Birhanli, Emre; Boran, Filiz; Bakar, Buesra; Ulu, Ahmet; Yesilada, Ozfer; Ates, Burhan
    In spite of many works on the biodegradation of textile dyes and phenolic compounds, we propose a new, inexpensive, environmentally friendly, and sustainable material based on electrospun fiber and immobilized laccase. The polycaprolactone (PCL)/polyethyleneimine (PEI) electrospun fibers were optimized and prepared by electrospinning technique according to the operational parameters like PCL concentration (12 wt%), PEI con-centration (10 wt%), voltage (16 kV), needle tip-collector distance (20 cm), and injection speed (0.7 mL/h). Next, characterization studies were performed to investigate the morphology and structure of the electrospun fibers without and with laccase. The crude laccase was obtained by cultivating the white rot fungus T. trogii (TT), and T. versicolor (TV). The resulting electrospun fibers showed a smooth surface with a mean diameter of around 560 nm, and larger diameters were observed after laccase immobilization. According to the results, immobili-zation increased the stability properties of laccase such as storage, and operational. For instance, the residual activity of the PCL/PEI/TTL and PCL/PEI/TVL after 10 repeated cycles, was 33.2 & PLUSMN; 0.2% and 26.0 +/- 0.9%, respectively. After 3 weeks of storage, they retained around 30% of their original activity. Moreover, the PCL/ PEI/TTL and PCL/PEI/TVL were found to possess high decolorization yield to remove Orange II and Malachite Green textile dyes from solutions imitating polluted waters. Among them, the PCL/PEI/TTL exhibited the highest decolorization efficiencies of Orange II and Malachite Green after 8 continuous uses at pH 5 and a temperature of 50 C, reaching over 86%, and 46%, respectively. Moreover, PCL/PEI/TTL and PCL/PEI/TVL effectively degraded the 2,6-dichlorophenol phenolic compound at an optimal pH and temperature range and exhibited maximum removal efficiency of 52.6 +/- 0.1% and 64.5 +/- 7.6%, respectively. Our approach combines the ad-vantageous properties of electrospun fiber material and immobilization strategy for the efficient use of industrial scale important enzymes such as laccase in various enzymatic applications.